To zoom out (ha!) from the problem a bit: web-usable 3D visualisation is probably best done with an idiomatic 3D technology; back in 2004, VRML, now X3D or similar. There are easy ways to visualise STL in a web context, and PDL can output STL today. PDL is intended to do X3D Real Soon Now™; see IndexedFaceSet to 3D lines in two lines of PDL.